JPH03173488A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To improve heat dissipation to a heat sink without exerting adverse influence upon laser characteristics, by constituting a clad layer in such a way that the heat sink side part has a composition whose thermal conductivity is higher than the active layer side. CONSTITUTION:A semiconductor laser element has an active layer 13 and a clad layer 9 in a chip in contact with a heat sink 20, which clad layer is adjacent to the heat sink 20 side of the active layer 13. The clad layer 9 is constituted of a first clad layer 21 formed on the active layer 13 side and a second clad layer 22 formed on the heat sink 20 side. The thermal conductivity of a second clad layer 22 is higher than that of the first clad layer 21. The above active layer 13, the active layer side part 21 of the clad layer 9, and the heat sink 20 side part 22 of the clad layer 9 are composed of the following, respectively; Ga1-xAlxAs, Ga1-yAlyAs, and Ga1-zAlzAs, where x<z<=y.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a semiconductor laser device intended for high-output operation, and more particularly to a semiconductor laser device with improved heat dissipation from a chip to a heat sink.

<Prior Art> Conventionally, this type of semiconductor laser device has a C5P (channeled substrate brainer) structure, as shown in FIG. This semiconductor laser device has n
After forming a trapezoidal trapezoid 111 with a width of 4 μm and a depth of 1.5 μm on the GaAs substrate 10 by etching, an n-type GaO, 5sio, etc. having a thickness of 0.2 μm outside the groove 11 was formed by liquid phase epitaxial growth. *sAS cladding layer 12 layer thickness 2. 08 μm thick non-doped Gao, e7AQ
a, +yAS active layer 13° p-type Gao with a thickness of 1 μm,
, 5A4o, +sAs cladding layer! 4 layers top 4 speed 2μm
N-type GaAs cap layers 15 are sequentially laminated. Furthermore, the groove 1 is formed using a SiO film (not shown) as a mask.
Width 47zm at the position corresponding to 1.

After forming a Zn diffusion region 16 extending to a depth of 2.2 μm and reaching the p-type cladding layer 14, low resistance electrodes 17.18 are formed on both sides of the
Heat sink 20 made of Cu with side electrode 18 facing down
It is fused onto the top with a solder 19 made of In. When current is applied between the picture electrodes 17 and 18, the current flows through the cap layer 15.
As a result, the flow concentrates in the p-type Zn diffusion portion 16 formed in the groove 11. in the active layer 13. Zn diffusion section 16
Laser oscillation is obtained in the oscillation region sandwiched between the two.

Then, the heat generated by laser oscillation is transferred to the active layer 1.
From the oscillation region of 3 to the p-type rad layer +4. Cap layer 15
, p (1111) is released to the heat sink 20 through the electric hli 18 and the solder 19.

<Problems to be Solved by the Invention> However, when the above-mentioned conventional semiconductor laser element is operated at a high output such as an optical output of 30 mW or more at the emission end facet, it becomes active due to non-radiative recombination at the emission end facet. The temperature near the end face of the layer locally rises to 150°C to 200°C (Todoroki et al., Journal of Applied Physics 581124 (1985)). Therefore, there is a problem that oxidation, which is a center of non-radiative recombination, progresses to the inside of the crystal of the chip, increasing the operating current, causing further heat generation, and having an adverse effect on long-term reliability.

In order to suppress such a local temperature rise, heat dissipation to the heat sink 20 must be improved. Here, the thermal conductivity and thickness of each layer from the active layer 13 to the heat sink 20 are as shown in FIG.

From the values shown in FIG. 5, the p-type cladding layer 14 has the lowest thermal conductivity among the layers;
It can be seen that 4 mainly hinders heat dissipation. This suggests that the composition of the p-type cladding layer 14 should be changed to increase its thermal conductivity. However, in order to effectively confine injected carriers and light, the composition of the cladding layer is originally determined from the viewpoint of the energy band gap difference and refractive index difference with respect to the active layer, and it cannot be easily changed. I can't. On the other hand, the thickness of the cladding layer is not necessarily 1 μm like the p-type rat layer 14 described above. However, simply reduce the thickness to 0.5 μm, for example.
If it is reduced to half below, the light generated in the active layer 13 will be distributed to the cap layer 15 and absorbed by the cap layer 15 made of GaAs, resulting in an increase in the oscillation threshold and a decrease in efficiency. This will adversely affect the laser characteristics.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a semiconductor laser device in which the structure of the cladding layer adjacent to the active layer is devised to skillfully direct heat dissipation to the heat sink without adversely affecting the laser characteristics. It's about doing.

Means for Solving the Problems> In order to achieve the above object 1), the present invention provides a semiconductor laser element having an active layer in a chip in contact with a heat sink and a cladding layer adjacent to the active layer on the heat sink side. The cladding layer is characterized in that the portion on the heat sink side has a higher thermal conductivity than the portion on the active layer side.

Further, the active layer, the active layer side portion of the cladding layer, and the heat sink side portion of the cladding layer are each made of Ga.
+-xA+2xAs, Ga+-yAQyAs, Ga+-
zAQzAs, preferably x<z<y.

Among the parts constituting the cladding layer, the part on the active layer side has the optimal composition for confining injected carriers and light as in the past, while the part on the heat sink side has a composition that is better than the part on the active layer side. Increase thermal conductivity. In this case, the injected carriers and light are effectively confined by the action of the active layer side portion, so that the laser characteristics are not adversely affected. Moreover, the effect of the heat sink side portion increases the heat dissipation effect compared to the conventional case.

Further, the active layer, the active layer side portion of the cladding layer, and the heat sink side portion of the cladding layer are each made of Ga.
+-xA12xAs, Ga+-yAQyAs, Ga+-
zAQzAs, and it is desirable that x<z<Y.

<Example> Hereinafter, the semiconductor laser device of the present invention will be explained in detail with reference to Examples.

FIG. 1 shows a first embodiment of the invention.

This semiconductor laser device includes an active layer 13 and an active fF
Cladding layer 9 adjacent to the heat sink 20 side of J 13
It is equipped with Components that are the same as those of the conventional semiconductor laser device shown in FIG. 4 are designated by the same numbers and their explanations will be omitted. The cladding WI9 has a p
The first cladding layer 21 made of type Gao, 5sA (2o, *sAS) and the p-type Ga provided on the heat sink 20 side
o, eA'2o, and *AS. Since lattice matching is achieved in this way, reliability can be improved.

The layer thicknesses of the first cladding layer 21 and the second cladding layer 22 are both 0.5 μm. The first cladding ff121 has the same composition as the p-type cladding layer 1-1 of the conventional semiconductor laser device, and can effectively confine injected carriers and light. Gao, 5AQo, and tAs constituting the second cladding layer 22 have thermal conductivities of 0 and l 6
W/cm-deg, which is approximately 1.5 times that of Gao, 5sAQa, and heAs that constitute the first cladding layer 21. Therefore, compared to the conventional semiconductor laser probe described above, heat dissipation to the heat sink 20 can be improved. In fact, it was possible to lower the temperature of the end face active layer from 180°C to 1500°C when outputting 40mW. In addition, stable operation for 5,000 hours was achieved at 40 mW, improving reliability.

FIG. 2 shows a second embodiment of the invention.

This semiconductor laser device is based on a structure called VSIS (V-channeled substrate inner stripe). Unlike the semiconductor laser device of the first embodiment, it is constructed on a p-type GaAs substrate 30, and has a current confinement layer 31 made of n-type GaAs and a current injection groove 32 inside.

Furthermore, p-type G a o , s s A Q o
, 43A cladding layer 33 made of S, and active layer 3 made of non-doped Gao, atA12o, +3As.
4, a cladding layer 29 made up of a first cladding layer 35 and a second cladding layer 36, and a cap layer made of n-type GaAs. 38° and 39 are p-side electrode and n
The side electrodes are shown, 40 is a screw made of In, and 41 is a heat sink made of Cu. The first cladding layer 35 is an n-type Gao, aAQo, provided on the active layer 34 side.
, aAS, while the second cladding layer 36 is provided on the heat sink 41 side and consists of nWGao, aA(2o, tA
It consists of s. In addition, the layer thickness is 0.4 μm,
0.6 μm. The first cladding layer 35 has a composition of Gao, hAQo, which has a large optical confinement effect. As
Therefore, the layer thickness can be reduced to 0.4 μm.

In addition, the thermal conductivity of Gaa, 4AQa, aA8 is Gao,
It is equivalent to 5sAQo and 4sA S.

Therefore, the heat dissipation effect can be enhanced due to the high thermal conductivity of Gao, eAQo, and yAs that constitute the second cladding layer. In fact, we were able to further reduce the end face temperature to 140° C. when outputting 40 mW.

FIG. 3(a) shows a third embodiment of the invention.

This semiconductor laser device uses molecular beam epitaxial (MB)
E) method or metal organic chemical vapor deposition (MOCVD) method is used to stack each layer. On an n-type GaAs substrate 50, first, a cladding layer 51 made of n-type Gao, 5sAQo, and asAs and an active layer 52 made of non-doped Gao, sF A12o, and +3AS are laminated. Next, as the cladding layer 49, p-type Gao, 1AQo, aA8 with a thickness of 0.3 μm is formed.
A first cladding layer 53 consisting of a p-type second cladding layer 54 having a thickness of 0.7 μm is laminated. As shown in FIG. 3(b), the composition of the second cladding layer 54 is continuously changed from Gao, aA(!o, eAs to GaAs) in the stacking direction. After stacking 55, a SiOy insulating film 56 is deposited, a stripe 57 for current injection is etched, and electrodes 58 and 59 are formed.Similar to the other embodiments, 60 and 61 are made of In. This figure shows a heat sink made of a screw material Cu.By using the MBE method or MOCVD method, the composition of the cladding layer 54 can be changed continuously.This semiconductor laser element also has a 40 m
The end face temperature at W output is as low as 140°C, demonstrating high reliability.

Note that, of course, the composition of the second cladding layer 54 may be changed not continuously but in steps.

<Effects of the Invention> As is clear from Section 2 below, the present invention provides a semiconductor laser device having an active layer in a chip in contact with a heat sink and a cladding layer adjacent to the active layer on the heat sink side. Since the layer has a composition that has a higher thermal conductivity on the heat sink side than on the active layer side, heat dissipation to the heat sink can be improved without adversely affecting laser characteristics.

Further, the active layer, the active layer side portion of the cladding layer, and the heat sink side portion of the cladding layer are each G
at-xA(!xAs, Ga(YAQ'/AG,
It is preferably made of G at-yAlyAs and Ga1-zAlzAs, and x<z<y.

[Brief explanation of the drawing]

Figures 1, 2, and 3 (a) are the 1st part of this invention. Second. 3(b) is a cross-sectional view showing the semiconductor laser device of the third embodiment. FIG. 3(b) is a diagram showing the AQ mix crystal ratio of each layer of the semiconductor laser device shown in FIG. 3(a). FIG. 5, which is a sectional view showing a semiconductor laser device, is a table showing the thermal conductivity and thickness of each layer constituting the conventional semiconductor device. 10.50-n-type GaAs substrate, ao=・p-type GaAs substrate, 9.12, 29, 33, 49.51... cladding layer,
13.34.52...Active layer, 21.35.53...First cladding layer, 22.36.
54...Second clad eyebrow, 15.37.55...Cap layer, 17.39.58-n side electrode, 18.38.59...p side electrode, +9.40.60... Screw material, 20.41.61... Heat sink, [1... Trapezoidal groove, 16... Zn diffusion part, 31... Current confinement layer, 32
...■-shaped groove, 56...SiOx insulating film, 57...current injection stripe. Figure 1 Figure 3 Figure 2 Figure 4

Claims (3)

[Claims] (1) In a semiconductor laser device having an active layer and a cladding layer adjacent to the heatsink side of the active layer in a chip in contact with a heatsink, the cladding layer has a portion closer to the heatsink than a portion closer to the active layer. A semiconductor laser device characterized in that it is composed of a composition having a higher thermal conductivity. (2) The active layer, the active layer side portion of the cladding layer, and the heat sink side portion of the cladding layer are each made of Ga.
_1-xAlxAs, Ga_1-yAlyAs, Ga_
2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is made of 1-zAlzAs, and x<z≦y. (3) The active layer, the active layer side portion of the cladding layer, and the heat sink portion of the cladding layer are each made of Ga.
_1-xAlxAs, Ga_1-yAlyAs, Ga_
Z consisting of 1-zAlzAs and z such that x<Z_1≦y
2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device decreases from _1 to Z_2, where Z_2≧0, continuously or stepwise.